The overflow box is ideally centered along the back and the wavebox centered on the side. Sealife, you will probably get a 1" wave if you center the overflow, 1/2"-3/4" with end overflows. I would use it with 2 6000's
Keeperz, I have no experience with a tank of this size, a wavebox is suitable for up to 320 gallons or so and you need an extension for every additional 320, the maximum being 1200 gallons or so (4 units total). End overflows is not a good idea if you can avoid it, they will be loud, they will shorten the wave substantially and the lack of water can have consequences for your sump and filter or closed loop system, remember no water will be going through the overflow when the trough of the wave is on that side and then it will get slammed with lots of water.